In a crypto world where more and more people are buying into more and more different kinds of altcoins, a centralized wallet system is becoming more in-demand.
It's a little ironic because crypto is decentralized, yet we're looking for centralized solutions.
I do believe that this is inevitable, simply because there's a demand and someone will try to supply.
It's not hard either. If you're on an exchange that supports multiple altcoins + btc, then that exchange already sort of acts as a "central wallet."
In that sense, you'd just need to make a hardware/online/desktop wallet with an interface that can access a backend that stores and manages multiple altcoins/bitcoin addresses and private keys. As I said, exchanges already do this... so if you just remove the trading aspect, then there you have a wallet that can do all this